Generally, a hybrid excavator includes an upper turning body which carries work elements, such as a boom, an arm, and a bucket. The hybrid excavator drives the boom and the arm while turning the upper turning body so that the bucket is moved to a desired work position.
A hybrid excavator which uses an electric motor as a source of power of a turning mechanism to turn the upper turning body is proposed (for example, refer to Patent Document 1 listed below). When decelerating the upper turning body, the electric motor is operated as a dynamo to generate electric power and the regeneration power is stored in an electrical power storage device.